In a conventional pedal module used for an accelerator for a vehicle, a pedal is turned forward by the action of a depressing force and is reversed by the urging force of a spring. Among the modules like this is a publicly known module that reverses the pedal from a forward position by the use of a double coil spring, as disclosed in Japanese patent document JP-A No. 2003-39970 (corresponding to U.S. Pat. No. 6,802,202).
In recent years, it is thought that a damping part 100 as shown in FIG. 16 is arranged in the pedal module using a double coil spring. To be specific, the damping part 100 is formed in the shape of a rectangular flat plate and is bent in the shape of a letter U and a middle portion in the direction of length is retained by an inside coil 111 of a double coil spring 110. Both end portions in the direction of length in the damping part 100 are formed into inserting portions 101 inserted between the inside coil 111 and an outside coil 112 of the double coil spring 110, respectively. These inserting portions 101 can prevent the establishment of resonance of the inside coil 111 and the outside coil 112 with external vibration. Further, these inserting portions 101 secure the gaps between the inside coil 111 and the outside coil 112 and prevent these coils 111 and 112 from being put into contact with each other. Hence, the double coil spring 100 can deliver desired spring characteristics.
Here, as for the respective inserting portions 101 of the damping part 100 shown in FIG. 16, attention is paid to their side end portions 102 in such a direction of width thereof (or peripheral direction of spring) that crosses the radial axis 113 of the double coil spring 110. As shown in FIG. 17, when the double coil spring 110 is compressed, first, the side end portions 102 of the respective inserting portions 101 abut against the outside coil 112 in a gap 114 between windings of the outside coil 112. This is caused by the fact that the side end portions 102 of the respective inserting portions 101 are apt to enter the gap 114 between the windings of the outside coil 112 before the double coil spring 110 shown in FIG. 16 is compressed. When the double coil spring 110 is further compressed from a state where the side end portions 102 abut against the outside coil 112 in the gap 114 between the windings, the side end portions 102 are sprung and disengaged from the outside coil 112. Impact caused at this time produces abnormal noises and propagates to the pedal to impair feeling of depressing the pedal.